1. Field of the Invention
The present invention relates to CMOS imaging arrays. More particularly, the present invention relates to low-leakage vertical multi-color CMOS imaging arrays.
2. The Prior Art
CMOS pixel sensors have become more prevalent in the art. Such pixel sensors typically employ a photodiode to collect charge and a select transistor and source-follower amplifier to read the charge out of the pixel sensor.
Multicolor versions of these pixel sensors are also known. Early examples of such sensors used an array of detectors formed in a pattern such as a Bayer pattern. Recently, vertical-color-filter CMOS pixel sensors have been disclosed, in which multiple pixel sensors (such as blue, green, and red) are positioned at different depths in a semiconductor body to take advantage of the fact that the penetration depth is a function of photon energy. Contact to the detectors disposed beneath the surface of the silicon body is made through deep contact structures. An example of such a pixel sensor arrangement is shown in U.S. Pat. No. 6,727,521.
One of the common problems associated with pixel sensors is leakage current at the surface of the silicon body in which the pixel sensors are fabricated. This problem is particularly troublesome with respect to the blue detector, which is located at or near the silicon surface.